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    <title>Document</title>
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    <canvas></canvas>

    <script>

        function draw() {
            var canvas = document.querySelector('canvas')
            if (canvas.getContext) {
                var ctx = canvas.getContext('2d');

                // 二次贝塞尔曲线
                ctx.beginPath();
                ctx.moveTo(75, 25);
                ctx.quadraticCurveTo(25, 25, 25, 62.5);
                ctx.quadraticCurveTo(25, 100, 50, 100);
                ctx.quadraticCurveTo(50, 120, 30, 125);
                ctx.quadraticCurveTo(60, 120, 65, 100);
                ctx.quadraticCurveTo(125, 100, 125, 62.5);
                ctx.quadraticCurveTo(125, 25, 75, 25);
                ctx.stroke();
            }
        }
        draw()
    </script>
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